Systems for treating wastewater in a series of filter-containing tanks

ABSTRACT

This invention relates to systems for treating wastewater and more particularly to removing nutrients from wastewater in a wastewater treatment system. Wastewater tanks, each having membrane filters, are arranged in series. Each tank is equipped with respective inlets and outlets and an air supply as well as detectors for monitoring various wastewater parameters. A controller is coupled to the detectors, inlets and outlets for effecting sequences of opening and closing the inlets and outlets and turning the air supplies on and off in response to various detecting conditions and effects different operations, including a cleaning mode, in different cycles.

This application claims benefit of U.S. Ser. No. 60/239,820, filed on Oct. 12, 2000.

FIELD OF THE INVENTION

This invention relates to processes and systems for treating wastewater and more particularly to removing nutrients from wastewater in a wastewater treatment process.

BACKGROUND OF THE INVENTION

The prior art has employed many devices and systems to process and purify water from industrial operations and municipal sources prior to discharging the water. Activated-sludge wastewater treatment plants (WWTP's), which are well known in the art, have been most often utilized to address this problem. Additionally, many industrial and municipal water treatment plants utilize biological systems to pre-treat their wastes prior to discharging into the usual municipal treatment plant. In these processes, the microorganisms used in the activated sludge break down or degrade contaminants for the desired water treatment. Efficient process performance and control requires quick and accurate assessment of information on the activity of microorganisms. This has proven to be a difficult task in view of the wide variety of materials and contaminants that typically enter into treatment systems. Also, variations in the quantity of wastewater being treated, such as daily, weekly or seasonal changes, can dramatically change numerous important factors in the treatment process, such as pH, temperature, dissolved oxygen, nutrients and the like, alteration of which can be highly detrimental to proper wastewater treatment. Improperly treated wastewater poses serious human health dangers.

Various biological nutrient removal (BNR) processes are currently used in wastewater treatment plants to assist in contamination degradation. In a typical BNR process, contaminants in the wastewater, such as carbon sources (measured as biochemical oxygen demand or BOD), ammonia, nitrates, phosphates and the like are digested by the activated sludge in anaerobic, anoxic and aerobic stages, also known in the art. In the anacrobic stage, the wastewater, with or without passing through a preliminary settlement process, is mixed with return activated sludge (RAS).

In many wastewater treatment plants one anaerobic stage is arranged in the BNR process. In the anaerobic stage poly-P microbial species take up short chain carbonaceous nutrient and store this nutrient intracellularly most commonly as polyhydroxybutyrate (PHB). Microorganisms must expend energy to accomplish this uptake of soluble organics and formation of intracellular storage products. The energy is obtained anaerobically through the cleavage of high energy phosphate bonds in stored long-chain inorganic polyphosphates. This process produces orthophosphate that is released from the cell into solution in the anaerobic zone. In a subsequent oxic stage, a rapid uptake of soluble orthophosphate provides for the resynthesis of the intracellular polyphosphates. Previously stored PHB is also aerobically metabolized to carbon dioxide, water, and new cells. When solids are wasted from the treatment process, the orthophosphate taken up by the poly-P microbes results in up to four times the phosphorus removal in comparison to a conventional treatment process without an anaerobic zone.

In most wastewater treatment plants, one or several anoxic stages are arranged in the BNR process. In the anoxic stages, denitrifiers, i.e., microbial species capable of denitrification, utilize nitrate and/or nitrite as electron acceptors and consume some of the available carbon sources during the denitrification process. NO_(x) is reduced stepwise to nitrogen gas and released to the atmosphere in the following manner:

NO₃ ⁻→NO₂ ⁻→NO→N₂O→N₂

The nitrate is usually supplied by recycling a certain volume of wastewater from the end of the oxic stage back to the beginning of the anoxic stage.

One or several oxic stages are typically employed in BNR processes. In the oxic stage, air which contains about 20% oxygen or pure oxygen, is supplied so that a desired dissolved oxygen level is maintained. Autotrophic organisms, i.e., microbial species capable of using ammonia as their energy source, convert ammonia to nitrite and nitrate under aerobic conditions. The poly-P microbial species in the wastewater uptake phosphate from the water phase and digest their intracellular PHB and PHV storage products converting it into polyphosphate, a compound for energy storage. The polyphosphate pool of the poly-P microbial species is thus replenished and phosphorous is removed from the water phase. The phosphorous is then removed from the system by sludge wasting, which is well known in the art. Under aerobic conditions, the remaining carbon sources in the water phase are further digested by aerobic organisms.

As the degradation of the contaminants nears completion, the microorganisms and the treated water are led through a solid/liquid separation process where the biosolids are separated from the liquid. The biosolids are then either recycled back to the anaerobic/anoxic/oxic treatment processes, or removed from the treatment process as waste biosolids. Common devices used in the solid/liquid separation are clarifiers where biosolids are settled to the bottom and withdrawn by recycling pumps while clear liquid flows over discharge weirs at the clarifier surface. Air flotation devices are also frequently used in the solid/liquid separation process. These are commonly known in the art.

However, many of the current wastewater treatment plants require clarifiers which increase the amount of space utilized by the wastewater treatment plant, add to the initial capital costs and increase operating and maintenance costs. Also, such systems oftentimes utilize significant operator input, which adds additional costs and, as mentioned above, utilize recycling/return systems which increase the capital costs, as well as the operating and maintenance costs. Finally, there is a significantly increased hydraulic retention time (HRT) in the overall treatment process.

SUMMARY OF THE INVENTION

In one aspect the invention relates to a system for removing BOD and NH₃ from wastewater including a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank outlet O₁ with a first tank membranous filter F₁, a second wastewater treatment tank T_(n−1) operatively connected to tank T₁ to permit wastewater to flow between tanks T₁ and T_(n−1), and an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank membranous filter F_(n) operatively connected to tank T_(n−1) to permit wastewater to flow between tanks T_(n−1) and T_(n).

There is also a NH₄ detector AD₁ connected to tank T₁, a NH₄ detector AD_(n) connected to tank T_(n), a TSS detector TD₁ connected to tank T₁, and a TSS detector TD_(n) connected to tank T_(n) and an air supply connected to at least one of said tanks.

A controller connects to an air supply, inlets I₁ and I_(n), outlets O₁ and O_(n), NH₃ detectors AD₁ and AD_(n), and TSS detectors TD₁ and TD_(n). The controller shifts between operational cycles C₁ and C₂, wherein in cycle C₁, I₁ and O_(n) are on, I_(n) is off and F₁ is in a cleaning mode until AD₁≧X or TD₁≦Y, wherein X and Y are selected concentrations of NH₃ and TSS, respectively, and wherein in cycle C₂, I_(n) and O₁ are on, I₁ is off and F_(n) is in a cleaning mode until AD_(n)≧X or TD_(n)≦Y.

In another aspect, the invention relates to a system for removing nutrients from wastewater including a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank O₁ with a first tank membranous filter F₁, an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank O_(n) with an Nth tank membranous filter F_(n), a second wastewater treatment tank T₂ operatively connected to tank T₁ to permit wastewater to flow between tanks T₁ and T₂ and having a second tank inlet I₂ connected to inlets I₁ and I_(n), a third wastewater treatment tank T₃ operatively connected to tank T₂ to permit wastewater to flow between tanks T₂ and T₃, and an N−1 wastewater treatment tank T_(n−1) operatively connected to tanks T₃ and T_(n) to permit wastewater to flow between tanks T₃ and T_(n−1) and between tanks T_(n−1) and T_(n), and having an N−1 tank inlet I_(n−1) connected to inlets I₁ and I_(n).

The system also includes an NH₃ detector AD₁ connected to tank T₁, an NH₃ detector AD_(n) connected to tank T_(n), a TSS detector TD₁ connected to tank T₁, a TSS detector TD_(n) connected to tank T_(n), an NO₃ detector ND₂ connected to tank T₂, an NO₃ detector ND_(n−1) connected to tank T_(n−1), and an air supply and/or mixing device connected to at least one of said tanks.

A controller connects to the air supply mixing device, inlets I₁, I₂, I_(n−1) and I_(n), outlets O₁ and O_(n), NH₃ detectors AD₁ and AD_(n), TSS detectors TD₁ and TD_(n), and NO₃ detectors ND₂ and ND_(n−1). The controller shifts between operational cycles C₁ and C₂, wherein, in cycle C₁, I₁ and O_(n) are on, I_(n) is off, F₁ is in a cleaning mode, and I₂ and I_(n−1) are on at j and k, wherein j and k are selected percentages of I₁, until 1) AD₁≧X or TD₁≦Y or 2) ND_(n−1)+AD_(n)≧Z, wherein X, Y and Z are selected concentrations of NH₃, TSS and NO₃+NH₃, respectively, and wherein in cycle C₂, I_(n) and O₁ are on, I₁ is off, F_(n) is in a cleaning mode, and I_(n−1) and I₂ are on at 1 and m, wherein 1 and m are selected percentages of I_(n), and wherein the air supply is shut off in T₂₊₁, when ND₂≧A is in cycle C₁ and in T_(n−2) when ND_(n−1)≧A is in cycle C₂, wherein A is a selected concentration of NO₃.

In yet another aspect, the invention relates to a system for removing phosphorus from wastewater including a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank outlet O₁ with a first tank filter F₁, an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank filter F_(n), a second wastewater treatment tank T₂ operatively connect to tank T₁ to permit wastewater to flow between tanks T₁ and T₂, a third wastewater treatment tank T₃ operatively connected to tank T₂ to permit wastewater to flow between tanks T₂ and T₃, an N−1 wastewater treatment tank T_(n−1) operatively connected to tanks T₃ and T_(n) to permit wastewater to flow between tanks T₃ and T_(n−1) and between tanks T_(n−1) and T_(n), a PO₄ detector PD₁ connected to tank T₁, a PO₄ detector PD_(n) connected to tank T_(n), a TSS detector TD₁ connected to tank T₁, a TSS detector TD_(n) connected to tank T_(n), an air supply and/or a mixing device connected to at least one of the tanks, and a controller connected to the air supply mixing device, inlets I₁ and I_(n), outlets O₁ and O_(n), PO₄ detectors PD₁ and PD_(n), TSS detectors TD₁ and TD_(n), and Filters F₁ and F_(n), the controller shifting between operational cycles C₁ and C₂, wherein, in cycle C₁, the air is off in T₁ and on in T_(n), I₁ and O_(n) are on and I_(n) and O₁ are off until 1) PD₁≦X or TD₁≦Y or 2) PD_(n)≧Z wherein X, Y, and Z are selected concentrations of PO₄, TSS, and PO₄, respectively, and wherein cycle C₂, the air is off in T_(n) and on in T₁, I_(n) and O₁ are on and I₁ and O_(n) are off until 1) PD_(n)≦X or TD_(n)≦Y or 2) PD₁≧Z, wherein X, Y, and Z are selected concentrations of PO₄, TSS, and PO₄, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a wastewater treatment system capable of removing organic material and ammonia.

FIG. 2 is a schematic of a preferred nutrient-removal system in accordance with additional aspects of the invention.

FIG. 3 is a schematic of a preferred phosphorus removal system.

DETAILED DESCRIPTION OF THE INVENTION

The following description is intended to refer to specific embodiments of the invention illustrated in the drawings and is not intended to define or limit the invention, other than in the appended claims. Also, the drawing is not to scale and various dimensions and proportions are contemplated.

Referring to FIG. 1, a system for removing biochemical oxygen demand (BOD) and/or NH₃/NH₄ ⁺ is shown. The system includes a tank T₁ located adjacent tank T_(n−1), which is located adjacent to tank T_(n). Although the tanks are shown directly adjacent to one another, it is not necessary that they be in contact, so long as they are operatively connected and that wastewater may flow between tanks T₁ and T_(n−1) on the one hand, and tanks T_(n−1) and T_(n) on the other hand. Also, all tanks should preferably include means to introduce air into the wastewater, such as with an air diffuser or the like.

Tank T₁ is connected to an influent line I₁ and tank T_(n) is connected to an influent line I_(n). Tank T₁ is connected to an outlet line O₁ and tank T_(n) is also connected to an outlet line O_(n). Each of the outlet lines O₁ and O_(n) connect to a filter unit which are preferably membranous-type filters, F₁ and F_(n), respectively. Also, each filter F₁ and F_(n) has a means for cleaning the filter, which (over time) can and/or does become laden with particulate matter. The particular details, structure and operation of the cleaning aspect of the filter is not important, so long as the cleaning capability is present.

Filters F₁ and F_(n) are membrane type filters which are depicted within Tanks T₁ and T_(n) but which do not necessarily have to be located within Tanks T₁ and T_(n) but which could be located outside of the tanks but operatively connected to tanks T₁ and T_(n) respectively.

Tank T₁ is provided with an NH₃/NH₄ ⁺ detector AD₁ as well as a TSS detector TD₁. Similarly, tank T_(n) is provided with an NH₃/NH₄ ⁺ detector AD_(n) and a TSS detector TD_(n). Preferred detectors AD are made by Myratek, Inc. and preferred detectors TD are made by Royce Instrumentation Corp., for example. It is also possible to supplement or substitute for detectors AD₁ and AD_(n) with OUR (oxygen uptake rate) detectors OD₁ and OD_(n) as shown in FIG. 1.

The system is also provided with a controller, which typically comprises an on-line computer system with appropriately programmed software, that connects to the various components I₁, I_(n), O₁, O_(n), AD₁, AD_(n), TD₁ and TD_(n) to monitor and control operation of the system. The controller operates in alternating cycles C₁ and C₂ depending on the detected conditions within the system. For example, in cycle C₁, inlet I₁ and outlet O_(n) are opened so that wastewater can flow into the system at tank T₁ and out of the system at tank T_(n). Inlet I_(n) is closed as is outlet O₁. Filter F₁ is most preferably caused to enter into a cleaning mode during each cycle, although it may not enter the cleaning mode on any given cycle depending on need or system set up.

The system operates in cycle C₁ until detector AD₁ or TD₁ detects a concentration of NH₃/NH₄ ⁺ or TSS, respectively, that is greater than or equal to selected concentrations X and Y, respectively. Representative values for concentration X include about 1 ppm to about 10 ppm, for example, and for concentration Y about 3000 ppm to about 20,000 ppm, although concentrations outside these ranges may be possible depending on the conditions. When those concentrations are exceeded, the controller switches from cycle C₁ to cycle C₂. Cycle C₂ changes a number of operational parameters wherein inlet I_(n) and outlet O₁ are opened to cause wastewater to flow into tank T_(n), through tank T_(n−1) and into tank T₁ and, finally, outwardly through outlet O₁. Inlet I₁ is closed as is outlet O_(n). Filter F_(n) is most preferably placed into a cleaning mode, although it may not enter the cleaning mode on any given cycle depending on need or system set up.

The system operates in cycle C₂ until detector AD_(n) or TD_(n) detects a concentration of NH₃/NH₄ ⁺ or TSS, respectively, greater than or equal to the selected concentrations X and Y, at which point the system switches back from cycle C₂ to cycle C₁. Typically, the concentrations X and Y vary from the ranges mentioned above, but can be outside of those ranges, depending on a wide variety of circumstances. Although the previous description contemplates the use of detectors and a controller to alternate between cycles C₁ and C₂, it is entirely possible that the alternating between cycles C₁ and C₂ could be initiated by timer control.

Referring to FIG. 2, another preferred nutrient-removal system is shown. FIG. 2 depicts a system having five separate tanks T₁, T₂, T₃, T_(n−1) and T_(n). While that particular system has five tanks, additional tanks are contemplated depending on the circumstances. In principal, the system of FIG. 2 operates similarly to the system of FIG. 1 except that it has a greater number of tanks and also has additional capabilities with respect to tanks T₂ and T_(n−1). Again, all tanks most preferably include means to introduce air into the wastewater as well as means to mix the tank contents without aeration.

In the same manner, as noted above, there are a series of adjacent tanks T₁ . . . T_(n) that are operatively connected to one another. As before, they need not literally be adjacent to one another, but are shown as such for matters of convenience and as a preferred form that minimizes the footprint of the system and construction materials. Wastewater is accordingly free to flow between the individual adjacent tanks, but ultimately is capable of flowing from tank T₁ to tank T_(n) and vice versa. Tanks T₁ and T_(n) have inlets I₁ and I_(n), as well as outlets O₁ and O_(n) as the previous system. The outlets are connected to the filter units in a manner similar to that shown in FIG. 1.

Tank T₂ is additionally provided with an NO₃ detector ND₂, as is tank T_(n−1) (ND_(n−1)). A preferred NO₃ detector may be obtained from Myratek, Inc., for example. Further, tanks T₂ and T_(n−1) are provided with a connection to inlets I₁ and I_(n) so that they are capable of receiving wastewater from either of those sources. The NO₃ detectors ND₂ and ND_(n−1), as well as the inlets I₂ and I_(n−1) are connected to the controller in addition to the inlets I₁ and I_(n), the outlets O₁ and O_(n), NH₃/NH₄ ⁺ detectors AD₁ and AD_(n) and TSS detectors TD₁ and TD_(n).

The system shown in FIG. 2 also operates in a two-cycle mode wherein in cycle C₁, inlet I₁ and outlet O_(n) are placed in the on position to receive wastewater into tank T₁ and discharge treated effluent from outlet O_(n). Inlet I_(n) is closed, as is outlet O₁. Preferably, filter F₁ is placed into the clean mode. However, additionally, j and k percent of the amount of wastewater flowing into tank T₁ through inlet I₁ is introduced into tanks T₂ and T_(n−1), respectively.

Cycle C₁ continues in operation until detector AD₁ detects concentrations of NH₃/NH₄ ⁺ greater than or equal to X, or detector TD₁ detects concentrations of TSS less than or equal to Y, at which point cycle C₁ switches to cycle C₂. As before, X and Y represent concentrations of NH₃/NH₄ ⁺ and TSS, respectively. Also, cycle C₁ switches to cycle C₂ when the additive concentration detected by detectors ND_(n−1)+AD_(n) exceeds or is equal to Z, which is the concentration of NO₃+NH₃ detected in tank T_(n−1).

Further, the controller is connected to the air supply system and, when the concentration A of NO₃ in tank T₂ exceeds a selected level, then the air supply is turned off in tank T₂₊₁. Air is off in tanks T₂ and T_(n−1) in cycle C₁.

Cycle C₂ includes opening inlet I_(n) and outlet O₁ such that wastewater enters into tank T_(n) and flows through the system towards tank T₁ and outwardly thereof. Inlet I₁ is off as is outlet O_(n). Preferably, the filter F_(n) is placed into the cleaning mode. Also, 1 and m percent of the quantity of wastewater flowing into tank T_(n) through inlet I_(n) is introduced into tanks T₂ and T_(n−1), respectively, through inlets I₂ and I_(n−1), wherein 1 and m are selected percentages of the total quantity of wastewater flowing through inlet I_(n). Air is off in tanks T₂ and T_(n−1) in cycle C₂.

The system continues to operate in cycle C₂ until detector AD_(n) or TD_(n) detect concentrations of NH₃/NH₄ ⁺ or TSS greater than or equal to X or less than or equal to Y, respectively, at which point cycle C₂ switches to cycle C₁. Similarly, the system switches from cycle C₂ to cycle C₁ when the concentration of NO₃ in tank T₂ plus the concentration of NH₃/NH₄ ⁺ in tank T₁ as detected by detectors ND₂ and AD₁ exceeds or is equal to Z, which is a selected concentration.

Finally, air is supplied to tank T_(n−2) until the concentration of NO₃ detected by detector ND_(n−1) is greater than or equal to concentration A, at which point air is then turned off.

Referring to FIG. 3, another preferred nutrient removal system is arranged to remove phosphorus. FIG. 3 depicts a system having 5 separate tanks, T₁, T₂, T₃, T_(n−1) and T_(n). While the depicted system has five tanks, any number of additional tanks are contemplated depending on the circumstances. In principal, the system of FIG. 3 operates similarly to the system of FIG. 1 except that it has a greater number of tanks and also has additional capabilities with respect to tanks T₁ and T_(n). Again, all tanks most preferably include means to introduce air into the wastewater as well as means to mix the tanks without aeration.

In the same manner, as noted above, there are a series of adjacent tanks T₁ . . . T_(n) that are operatively connected to each other. As before, they do not need to be literally adjacent to one another, but are shown as such for matters of convenience and as a preferred form that minimizes the footprint of the system. Wastewater is accordingly free to flow between the individual tanks but ultimately is capable of flowing from tank T₁ to tank T_(n) and vice versa. Tanks T₁ and T_(n) have inlets I₁ and I_(n) as well as outlets O₁ and O_(n) as the previous system. The outlets are connected to the filter units in a manner similar to that shown in FIG. 1.

Tank T₁ is additionally provided with PO₄ detector, PD₁, as is tank T_(n)(PD_(n)). A preferred PO₄ detector is Chemscan, Inc. for example. Tanks T₁ and T_(n) are also equipped with TSS detectors. The PO₄ detectors, PD₁ and PD_(n) as well as the inlets, I₁ and I_(n), the outlets O₁ and O_(n), and TSS detectors TD₁ and TD_(n) are connected to the system controller.

The system shown in FIG. 3 also operates in a two-cycle mode wherein in cycle C₁, inlet I₁ and outlet O_(n) are placed in the “on” position to receive wastewater into tank T₁ and discharge effluent from outlet O_(n). Inlet I_(n) is closed as is outlet O₁. Preferably, filter F₁ is placed into the clean mode.

Cycle C₁ continues in operation until detector PD₁ detects a concentration of phosphate less than or equal to X, or detector TD₁ detects a concentration of Tss less than or equal to Y or detector PD_(n) detects a concentration of phosphate greater than or equal to Z, at which cycle C₁ switches to cycle C₂. X and Z both represent certain concentrations of phosphate and Y represents a concentration of TSS.

Further, the controller is connected to the air supply and influent flow control system such that in cycle C₁, the air is off and anaerobic conditions are present in T₁ and I₁ and O_(n) are on. Also, the air is on in subsequent tanks T₂ through T_(n). In the same fashion, in cycle C₂, the air is off and anaerobic conditions are present in T_(n) and I_(n) and O₁ are on. Also, the air is on in subsequent tanks T_(n−1) through T₁.

Cycle C₂ includes opening inlet I_(n) and outlet O₁ such that wastewater enters into tank T_(n) and flows through the system towards tank T₁ and outwardly thereof. Inlet I₁ is off as is outlet O_(n). Preferably, the filter F_(n) is placed into the cleaning mode. Air is off in tank T_(n) and on in subsequent tanks in cycle C₂.

The system continues to operate in cycle C₂ until detector PD_(n) detects a concentration less than or equal to X or detector TD_(n) detects a concentration less than or equal to Y or detector PD₁ detects a concentration greater than or equal to Z, at which point cycle C₂ switches to cycle C₁.

The above two-cycle operation for the systems shown in FIGS. 1, 2 and 3, as well as other systems contemplated herein, although not shown in the drawings, provides significant advantages over prior systems. The above-described systems provide wastewater that is treated to the degree that it is “nearly” potable and could be rendered potable simply by passage of the water through a reverse osmosis membrane, for example. Additionally, the above systems do not require the utilization of clarifiers which are commonly used in prior art wastewater treatment systems. This provides the advantage of having an overall system with a smaller footprint, greater reliability, reduced capital expenditures as well as operational and maintenance costs.

Also, the above-described systems can be highly automated, which reduces the amount of human operator attention required, thereby further reducing operational costs and further reducing operational uncertainties.

A still further advantage in the reduction of initial capital investment as well as operational costs is the elimination of the traditional recycle/return systems utilized in conventional systems. Also, elimination of such recycle/return systems results in an increase in HRT relative to conventional systems.

Also, by preselecting or setting the various detector levels, the treated water can virtually be assured of compliance with permits for the particular facility at issue. Finally, the system provides for the capability of nutrient removal, which is lacking in many of the prior art systems and provides for the ability to achieve and maintain higher MLSS concentration, i.e. 2-3 times that of conventional systems, thereby resulting in an increase in treatment capacity per unit volume.

Although this invention has been described with reference to specific forms of apparatus and method steps, it will be apparent to one of ordinary skill in the art that various equivalents may be substituted, the sequence of steps may be varied, and certain steps may be used independently of others, all without departing from the spirit and scope of the invention defined in the appended claims. 

What is claimed is:
 1. A system for removing BOD and NH₃ from wastewater comprising: a) a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank outlet O₁ with a first tank filter F₁; b) another wastewater treatment tank T_(n−1) operatively connected to tank T₁ to permit wastewater to flow between tanks T₁ and T_(n−1); c) an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank filter F_(n) operatively connected to tank T_(n−1) to permit wastewater to flow between tanks T_(n−1) and T_(n); d) a NH₃detector AD₁ connected to tank T₁; e) a NH₃ detector AD_(n) connected to tank T_(n); f) a TSS detector TD₁ connected to tank T₁; g) a TSS detector TD_(n) connected to tank T_(n); h) an air supply connected to at least one of said tanks; and i) a controller connected to an air supply inlets I₁ and I_(n), outlets O₁ and O_(n), filters F₁ and F_(n), NH₃ detectors AD₁ and AD_(n), and TSS detectors TD₁ and TD_(n), the controller shifting between operational cycles C₁ and C₂, wherein in cycle C₁, I₁ and O_(n) are on, and I_(n) is off until AD₁≧X or TD₁≦Y, wherein X and Y are selected concentrations of NH₃ and TSS, respectively, and wherein in cycle C₂, I_(n) and O₁ are on, and I₁ is off until AD_(n)≧X or TD_(n)≦Y.
 2. The system of claim 1, wherein filter F₁ is in a cleaning mode in cycle C₁.
 3. The system of claim 1, wherein filter F_(n) is in a cleaning mode in cycle C₂.
 4. The system of claim 1, wherein filters F₁ and F_(n) are membrane filters.
 5. The system of claim 4, wherein filters F₁ and F₃ are hollow fiber membrane filters.
 6. The system of claim 1, further comprising an air supply connected to said controller and adapted to supply air to one or more of said tanks.
 7. A system for removing NH₃ from wastewater comprising: a) a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank let O₁ with a first tank filter F₁; b) another wastewater treatment tank T_(n−1) operatively connected to tank T₁ to permit wastewater to flow between tanks T₁ and T_(n−1); c) an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank filter F_(n) operatively connected to tank T_(n−1) to permit wastewater to flow between tanks T_(n−1) and T_(n); d) a NH₃ detector AD₁ connected to tank T₁; e) a NH₃ detector AD_(n) connected to tank T_(n); f) an air supply connected to at least one of said tanks; and g) a controller connected to an air supply inlets I₁ and I_(n), outlets O₁ and O_(n), filters F₁ and F_(n), and NH₃ detectors AD₁ and AD_(n), the controller shifting between operational cycles C₁ and C₂, wherein in cycle C₁, I₁ and O_(n) are on, and I_(n) is off until AD₁≧X, wherein X is a selected concentration of NH₃ and wherein in cycle C₂, I_(n) and O₁ are on and I₁ is off until AD_(n)≧X.
 8. The system of claim 7, wherein filter F₁ is in a cleaning mode in cycle C₁.
 9. The system of claim 7, wherein filter F_(n) is in a cleaning mode in cycle C₂.
 10. The system of claim 7, wherein filters F₁ and F_(n) are membrane filters.
 11. The system of claim 7, wherein filters F₁ and F₃ are hollow fiber membrane filters.
 12. The system of claim 7, further comprising an air supply connected to said controller and adapted to supply air to one or more of said tanks.
 13. A system for removing BOD from wastewater comprising: a) a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank outlet O₁ with a first tank filter F₁; b) another wastewater treatment tank T_(n−1) operatively connected to tank T₁ to permit wastewater to flow between tanks T₁ and T_(n−1); c) an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank filter F_(n) operatively connected to tank T_(n−1) to permit wastewater to flow between tanks T_(n−1), and T_(n); d) a TSS detector TD₁ connected to tank T₁; e) a TSS detector TD₃ connected to tank T_(n); f) a OUR detector OD₁ connected to tank T₁; g) a OUR detector OD₃ connected to tank T_(n); h) an air supply connected to at least one of said tanks; and i) a controller connected to an air supply inlets I₁ and I_(n), outlets O₁ and O_(n), TSS detectors TD₁ and TD_(n), OUR detectors OD₁ and OD_(n), and filters F₁ and F_(n), the controller shifting between operational cycles C₁ and C₂, wherein in cycle C₁, I₁ and O_(n) are on, and I_(n) is off until TD₁≦Y or OD₁≧X wherein Y is a selected concentration of TSS and X is a selected OUR, and wherein in cycle C₂, I₃ and O₁ are on and I₁ is off until TD_(n)≦Y or OD_(n)≧X.
 14. The system of claim 13, wherein filter F₁ is in a cleaning mode in cycle C₁.
 15. The system of claim 13, wherein filter F_(n) is in a cleaning mode in cycle C₂.
 16. The system of claim 13, wherein filters F₁ and F_(n) are membrane filters.
 17. The system of claim 13, wherein filters F₁ and F₃ are hollow fiber membrane filters.
 18. The system of claim 13, further comprising an air supply connected to said controller and adapted to supply air to one or more of said tanks.
 19. A system for removing nutrients from wastewater comprising: a) a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank outlet O₁ with a first tank filter F₁; b) an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank filter F_(n); c) a second wastewater treatment tank T₂ operatively connected to tank T₁ to permit wastewater to flow between tanks T₁ and T₂ and having a second tank inlet I₂ connected to inlets I₁ and I_(n); d) a third wastewater treatment tank T₃ operatively connected to tank T₂ to permit wastewater to flow between tanks T₂ and T₃; e) an N−1 wastewater treatment tank T_(n−1) operatively connected to tanks T₃ and T_(n) to permit wastewater to flow between tanks T₃ and T_(n−1) and between tanks T_(n−1) and T_(n), and having an N−1 tank inlet I_(n−1) connected to inlets I₁ and I_(n); f) an NH₃ detector AD₁ connected to tank T₁; g) an NH₃ detector AD_(n) connected to tank T_(n); h) a TSS detector TD₁ connected to tank T₁; i) a TSS detector TD_(n) connected to tank T_(n); j) an NO₃ detector ND₂ connected to tank T₂; k) an NO₃ detector ND_(n−1) connected to tank T_(n−1); l) an air supply connected to at least one of said tanks; m) a mixing device connected to at least one of said tanks; and n) a controller connected to the air supply mixing device, inlets I₁, I₂, I_(n−1) and I_(n), outlets O₁ and O_(n), NH₃ detectors AD₁ and AD_(n), TSS detectors TD₁ and TD_(n), NO₃ detectors ND₂ and ND_(n−1), and filters F₁ and F_(n), the controller shifting between operational cycles C₁ and C₂, wherein, in cycle C₁, I₁ and O_(n) are on and I_(n) is off, and I₂ and I_(n−1) are on at j and k, wherein j and k are selected percentages of I₁, until 1) AD₁≧X or TD₁≦Y, or 2) ND_(n−1)+AD₁≧Z, wherein X, Y and Z are selected concentrations of NH₃, TSS and NO₃+NH₃, respectively, and wherein in cycle C₂, I_(n) and O₁ are on and I₁ is off, and I_(n−1) and 12 are on at 1 and m, wherein 1 and m are selected percentages of I_(n), and wherein the air supply is shut off in T₂₊₁ when ND₂≧A is in cycle C₁ and in T_(n−2) when ND_(n−1)≧A is in cycle C₂, wherein A is a selected concentration of NO₃.
 20. The system of claim 19, wherein filter F₁ is in a cleaning mode in cycle C₁.
 21. The system of claim 19, wherein filter F_(n) is in a cleaning mode in cycle C₂.
 22. The system of claim 19, wherein filters F₁ and F_(n) are membrane filters.
 23. The system of claim 19, wherein filters F₁ and F_(n) are hollow fiber membrane filters.
 24. A system for removing phosphorus from wastewater comprising: a) a first wastewater treatment tank T₁ having a first tank inlet I₁ and a first tank outlet O₁ with a first tank filter F₁; b) an Nth wastewater treatment tank T_(n) having an Nth tank inlet I_(n) and an Nth tank outlet O_(n) with an Nth tank filter F_(n); c) a second wastewater treatment tank T₂ operatively connect to tank T₁ to permit wastewater to flow between tanks T₁ and T₂; d) a third wastewater treatment tank T₃ operatively connected to tank T₂ to permit wastewater to flow between tanks T₂ and T₃; e) an N−1 wastewater treatment tank T_(n−1) operatively connected to tanks T₃ and T_(n) to permit wastewater to flow between tanks T₃ and T_(n−1) and between tanks T_(n−1) and T_(n); f) a PO₄detector PD₁ connected to tank T₁; g) a PO₄ detector PD_(n) connected to tank T_(n); h) a TSS detector TD₁ connected to tank T₁; i) a TSS detector TD_(n) connected to tank T_(n); j) an air supply and/or a mixing device connected to at least one of said tanks; and k) a controller connected to the air supply mixing device, inlets I₁ and I_(n), outlets O₁ and O_(n), PO₄ detectors PD₁ and PD_(n), TSS detectors TD₁ and TD_(n), and Filters F₁ and F_(n), the controller shifting between operational cycles C₁ and C₂, wherein, in cycle C₁, the air is off in T₁ and on in T_(n), I₁ and O_(n) are on and I_(n) and O₁ are off until 1) PD₁≦X or TD₁≦Y or 2) PD_(n)≧Z wherein X, Y, and Z are selected concentrations of PO₄, TSS, and PO₄, respectively, and wherein cycle C₂, the air is off in T_(n) and on in T₁, I_(n) and O₁ are on and I₁ and O_(n) are off until 1) PD_(n)≦X or TD_(n)≦Y or 2) PD₁≧Z, wherein X, Y, and Z are selected concentrations of PO₄, TSS, and PO₄, respectively.
 25. The system of claim 24, wherein filter F₁ is in cleaning mode in cycle C₁.
 26. The system of claim 24, wherein filter F_(n) is in cleaning mode in cycle C₂.
 27. The system of claim 24, wherein filters F₁ and F_(n) are membrane filters.
 28. The system of claim 24, wherein filters F₁ and F_(n) are hollow fiber membrane filters.
 29. The system of claim 24, further comprising an air supply connected to said controller and adapted to supply air to one or more of said tanks. 